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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id y11-20020a05620a44cb00b006a37eb728cfsm31585444qkp.1.2022.07.08.13.49.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Jul 2022 13:49:03 -0700 (PDT) Date: Fri, 8 Jul 2022 13:48:46 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: Nadav Amit cc: Hugh Dickins , LKML , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "x86@kernel.org" , Linux MM , Dave Hansen , Peter Zijlstra , Andy Lutomirski , Andrew Morton Subject: Re: [PATCH] x86/mm/tlb: ignore f->new_tlb_gen when zero In-Reply-To: <49C173B5-CF12-44AA-BE00-689E99E65C23@vmware.com> Message-ID: <23b7e5f8-8b38-51aa-fecd-3ed92118af72@google.com> References: <20220708003053.158480-1-namit@vmware.com> <4eccbb3a-2b5a-039-e934-da451e469929@google.com> <49C173B5-CF12-44AA-BE00-689E99E65C23@vmware.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="0-2142999139-1657313342=:1568" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657313344; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=FBvdmM502BDBY4F9Apm5h9KKjB4dWv/nkjvzfkcviig=; b=ph8lTvmSXk5F1MUfhDjp8wyXf7PUjWq4ufGJmHbtuakBN2yZR15OmWz4KCqfIs4JFMsFYZ 1jybVPV8RiIZMV4cIGhZ9CKGsNtFtLE4sz757Fl8mHGuhH/VeZyD6UUISamG4RpL1N1sl4 O9iQ7h5Rkaf0CNmw3j6fOZSAEqzKMj0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657313344; a=rsa-sha256; cv=none; b=qPBVQI77CWImpc/gXBmomEmX0ZqpXeG88hHR4WsbQ3tXj4sfP4NpMfMt5Rac5Qo5RiLoQd VzIJ4iDeW/yI5qC9/r2/AVMbu8RCkget08JUgudjyUntDDF6LkliguMsdQfi3gDJ+PS8Wh Nr625II0+E5DA0zMYHpoWSC7mP9VQsU= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=flRZHbrF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf05.hostedemail.com: domain of hughd@google.com designates 209.85.222.172 as permitted sender) smtp.mailfrom=hughd@google.com Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=flRZHbrF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf05.hostedemail.com: domain of hughd@google.com designates 209.85.222.172 as permitted sender) smtp.mailfrom=hughd@google.com X-Stat-Signature: 1zmk8hgipz53ibicfyrsaegiq9o3dyur X-Rspamd-Queue-Id: 19C41100025 X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1657313343-525968 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --0-2142999139-1657313342=:1568 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 8 Jul 2022, Nadav Amit wrote: > On Jul 8, 2022, at 12:21 PM, Hugh Dickins wrote: >=20 > > =E2=9A=A0 External Email > >=20 > > On Thu, 7 Jul 2022, Nadav Amit wrote: > >=20 > >> From: Nadav Amit > >>=20 > >> Commit aa44284960d5 ("x86/mm/tlb: Avoid reading mm_tlb_gen when > >> possible") introduced an optimization of skipping the flush if the TLB > >> generation that is flushed (as provided in flush_tlb_info) was already > >> flushed. > >>=20 > >> However, arch_tlbbatch_flush() does not provide any generation in > >> flush_tlb_info. As a result, try_to_unmap_one() would not perform any > >> TLB flushes. > >>=20 > >> Fix it by checking whether f->new_tlb_gen is nonzero. Zero value is > >> anyhow is an invalid generation value. > >>=20 > >> In addition, add the missing unlikely() and jump to get tracing right. > >>=20 > >> Fixes: aa44284960d5 ("x86/mm/tlb: Avoid reading mm_tlb_gen when possib= le") > >> Reported-by: Hugh Dickins > >> Cc: Dave Hansen > >> Cc: Peter Zijlstra (Intel) > >> Cc: Andy Lutomirski > >> Signed-off-by: Nadav Amit > >=20 > > Thanks a lot for your rapid response and thinking it through > > (before I got around to any "nopcid" or "nopti" experiments). > >=20 > > I've been testing this one for a few hours now, and no problems seen. > > I expect you'll be sending another version, maybe next week, meeting > > Dave's concerns; but wanted to reassure that you have correctly > > identified the issue and fixed it with this - thanks. >=20 > Thanks, Hugh. Sorry again for my mistake. >=20 > Can I please have your =E2=80=9CTested-by=E2=80=9D? Sure, let me scrabble around in my box of tags, yes, here's one: Tested-by: Hugh Dickins --0-2142999139-1657313342=:1568--